Imager::Graph depends on Imager, since
you probably want text on your graph you will also need one of the
font libraries supported by Imager, and a suitable font. The ImUgly
TrueType font is included, but it's pretty ugly as the name
implies.

The tests require both TrueType and PNG support, but this is mainly
required so I can avoid supplying huge test comparison images, and so
I don't need to supply an extra (relatively large) font file.